Fibrillar Fines Research Articles

Production of low-density and high-strength paperboards by controlled micro-nano fibrillation of fibers

One of the critical challenges in the fiber-based packaging industry is to produce low-density paperboards with high functionality and attractive cost structure. In this study, we examine how control of the hierarchical fiber swelling can be used to enhance bonding and generate a low-density fiber network with excellent strength properties. Here, the osmotic pressure inside the cell wall is increased by adding phosphate groups with a deep eutectic solvent (DES) functional drying method. Together with mechanical refining, this process causes the fibril aggregates to split and swell up massively. This effect was measured by a novel thermoporosimetry analysis method. The treated fibers have enhanced external fibrillation, fibrillar fines and bonding potential. When mixed with relatively stiff, unrefined fibers, a well-bonded sheet with lower density than a conventionally refined reference sheet was achieved. The results suggest that pulp fibers can be “nanoengineered” to enhance performance without the complications of producing and adding nanocellulose.

Fibre development in an intensified mechanical pulping process

Abstract Mechanical pulp for printing paper can be produced with a process that involve much less equipment and that require much lower specific energy compared to conventional processes. Even though common evaluation methods, e.g. handsheet testing, have shown that the pulp quality is similar for the simplified and the conventional processes, it is not known how fibre properties, at the microscopic level, is developed with the simplified process. In this mill scale study, the fibre properties attained with an “intensified” mechanical pulping process, consisting of single stage high consistency double disc refining followed by two stage low consistency refining and no reject treatment was investigated. The simplified process was compared to a process with a reject system. The simplified process rendered fibres with higher degree of fibrillation, higher share of axial splits, lower fibre wall thickness but slightly lower length than the conventional process. The fibrillar fines size distribution of the two processes was different. The conventional process generated more of small fibrillar fines which probably explains the higher tensile index at given density for that process. The results show that it is possible to simplify the production process for mechanical pulp and reduce the specific energy with over 700 kWh/adt.

Low-consistency refining of CTMP targeting high strength and bulk: effect of filling pattern and trial scale

Abstract Chemithermomechanical pulp (CTMP) is often used in central layers of multiply paperboards due to its high bulk and strength. Such a CTMP should consist of well-separated undamaged fibres with sufficient bonding capacity. The basic objective of this work is to optimize process conditions in low-consistency (LC) refining, i. e. to select or ultimately develop new optimal LC refiner filling patterns, in order to produce fibrillar fines and improve the separation of fibres from each other while preserving the natural fibre morphology as much as possible. Furthermore, the aim is to evaluate if this type of work can be done at laboratory-scale or if it is necessary to run trials in pilot- or mill-scale in order to get relevant answers. First stage CTMP made from Norway spruce (Picea abies) was LC refined in mill-, pilot- and laboratory-scale trials and with different filling patterns. The results show that an LR1 laboratory refiner can favourably be used instead of larger refiners in order to characterize CTMP with regard to tensile index and z-strength versus bulk. A fine filling pattern resulted in CTMP with higher tensile index, z-strength and energy efficiency at maintained bulk compared to a standard filling pattern.

Fines mobility and distribution in streaming fibre networks: experimental evidence and numerical modeling

The motion of flocculated fibres in a streaming suspension is governed by the balance of the network strength and hydrodynamic forces. With increasing flow rate through a channel, (1) the network initially occupying all space, (2) is then compressed to the centre, and (3) ultimately dispersed. This classical view neglects fibres-fines: we find that the distribution of these small particles differs in streaming suspensions. While it is known that fibre-fines can escape the fibre network, we find that the distribution of fibre-fines is non-homogenous in the network during compression: fibre-fines can be caged and retarded in the streaming fibre network. Hence, the amount of fibre-fines is reduced outside of a fibre network and enriched at the network’s interface. Aiming on selectively removing fibre-fines from a streaming network by suction, we identify a reduction of the fines removal rate. That documents a hindered mobility of fibre-fines when moving through the network of fibres. Additionally, we found evidence, that the mobility of fibre-fines is dependent on the fibre-fines quality, and is higher for fibrillar fines. Consequently, we suggest that the quality of fibre-fines removed from the suspension can be controlled with the flow regime in the channel. Finally, we present a phenomenological model to compute the length dependent fibre distribution in an arbitary geometry. For a fibre suspension channel flow we are able to predict a length-dependent fibre segregation near the channel’s centre. The erosion of a plug of long fibres was however underestimated by our model. Interestingly, our model with parameters fitted to streaming fibre suspension qualitatively agreed with the motion of micro-fibrillated cellulose. This gives hope that devices for handling flocculated fibre suspensions can be designed in the future with greater confidence.

Impact of stone ground ‘V-fines’ dispersion and compatibilization on polyethylene wood plastic composites

Recent studies have suggested that blocky mechanical pulp fines (CTMP fines) and fibrillar fines (SMC fines) have a negative impact on biocomposite modulus of rupture (MoR) in compression molded biocomposites. In addition, it was suggested that CTMP fines also have a negative impact on biocomposite modulus of elasticity (MoE). This study investigated whether these findings transfer to other types of cellulose fines material and injection molding. The effect of ‘V-fines’ addition to sawdust- and TMP-based biocomposites was analyzed, with respect to fines concentration, dispersing agent, and compatibilizers. The results indicated that the addition of ‘V-fines’ increased the stiffness (MoE) of all the analyzed compositions, while reducing the elongation at break. The addition of ‘V-fines’ reduced the tensile and flexural strength of TMP biocomposites, while it was largely unaffected for sawdust biocomposites. Flexural strength for neat ‘V-fines’ composites showed an increase that was proportional to the remaining pulp fibers composition. The addition of a dispersant agent to the ‘V-fines’ increased tensile strength, suggesting that an increased dispersion of the ‘V-fines’ can be achieved and is beneficial to the composite. The effects of the analyzed compatibilizer (polyethyleneoxide) was negligible, except for a small indication of increased MoE for fines / sawdust biocomposites.

The influence of fines material on the mechanical performance of wood fiber polypropylene composites

With an increasing interest in a wider scope of biomass feedstocks for biocomposite production, the potential influence of a possibly higher proportion of fines material needs to be addressed. In the pulp and paper industry, at least two major classes of fines material are identified; blocky fines and fibrillar fines. These differ in their aspect ratio, with the later having substantially higher aspect ratio. In this study, the physical impact of blocky fines (from CTMP refining) and fibrillar fines (produced via Super® Masscolloider refining) on a wet formed compression molded polypropylene (PP) matrix biocomposites were compared. The results indicated that in wet formed compression molded polymer matrix composites, both blocky (CTMP) and fibrillar (SMC) fines have a significant negative impact on modulus of rupture (MoR). Additionally, blocky CTMP fines also have a significant negative impact on modulus of elasticity (MoE). It is postulated that this is due to fibril agglomeration, in the case of fibrillar fines, and low aspect ratio in combination with some agglomeration, in the case of blocky CTMP fines. The indication is that fines material that has not been treated to minimize agglomeration has limited benefits as a reinforcing agent, and only a negative impact on most properties in wet formed compression molded polymer matrix composites.

Localization of cellulosic fines in paper via fluorescent labeling

Generated in the pulp and paper production process, cellulosic pulp fines are fibrous cellulosic materials capable of passing a 200 mesh screen. Processed pulp fines remain in the pulp and affect pulp and paper sheet properties. Their specific morphology promotes interactions with fibers and alters sheet properties. Nevertheless, the 3D distribution of fines in paper sheets has not been revealed so far. Localizing fines within a matrix of fibers is challenging since both elements have the same chemical composition and fines have small dimensions. It is required to increase the contrast of pulp fines, while avoiding any alteration of initial fines morphology. In this study, fines were first separated and labeled with Rhodamine B isothiocyanate, a fluorescent dye. Labeled fines were blended with pulp at different concentrations and paper sheets were produced from each mixture. Prior to imaging, pulps and handsheets were characterized by standard pulp and paper tests and compared with references, showing no significant differences between sheets containing labeled and untreated fines. Thus, mechanical and physical tests indicated that no, or only minor alteration of fines properties by the labeling process occurred. We then applied two imaging techniques to detect the labeled pulp fines in the paper network, namely confocal laser scanning microscopy and multiphoton microscopy, visualizing the 3D distribution of fluorescent fines within the fiber network. The results obtained also allowed a differentiation between morphologically different fines showing fiber fragments more attached to single fibers whereas more fibrillar fines concentrate in fiber–fiber joints, thereby strengthening bonding.Graphic abstract

Mechanisms of strength and stiffness improvement of paper after PFI refining with a focus on the effect of fines

Refining (i.e., mechanical beating of pulp) is a common procedure that is used in paper-making to improve the mechanical properties of the final product. The improvements caused by refining are mainly attributed to increased density and to a better bonding between fibers. In this work, we study how various mechanisms that can be triggered by refining affect the tensile behavior of the sheets. Consequently, we use direct numerical simulations of fiber networks. We relate our finding to the experimental measurements that we conducted on handsheets. We have found that fibrillar fines with size distributions below the resolution of modern state-of-the art pulp characterization tools have a substantial contribution to the increased strength and stiffness of the sheets.

New technology for producing fibrillar fines directly from wood

A method for producing lignocellulosic fibrillar fines directly from moist wood through a grinding process was evaluated. The method is based on a conventional stone wood grinding process with a novel grinding stone surface structure. The grinding stone (wheel) with a surface profile serrated in the axial direction of the wheel, forces fibres to break down into fibrils instead of detaching as fibres from the wood matrix. The arrangement mimics the inclined feeding of a log against a grinding stone and is completed without any related technical difficulties. Typically over a 90% conversion rate to fines (passing the Standard Mesh 200 wire) were achieved. The characteristics of the fines were influenced by the details of the surface structures, the velocity of the grinding stones, the feeding rate of the woods, and the specific energy consumption. This method enables novel means to adjusting the structure and properties of paper and paperboard products, as well as those of novel fibre and fibre-composite products.

Fiber- and fine fractions-derived effects on pulp quality as a result of mechanical pulp refining consistency

High-yield pulping of wood chips using low-consistency (LC) refining in combination with primary-stage high-consistency (HC) refining has previously been shown to produce paper with quality parameters (tensile strength and light-scattering coefficient) commonly targeted for newsprint with significantly less refining energy input than using only HC refining. However, questions remain on the differences in the refining action between the two refiner types and for high-yield pulping, the refiner energy demand is a crucial process parameter. Therefore, fines- and fiber-fraction development in HC and LC refining has been studied in detail using Bauer-McNett fractionation, and the respective tensile strengths of the different fractions have been compared. Quantitative and qualitative (morphological) characteristics of the isolated fine fractions have also been analyzed in detail using a newly developed automated fluorescence microscopy method and scanning electron microscopy. The results suggest the difference in LC/HC pulp properties (strength and optical) is partly derived from deviating fiber and fines morphologies and mass balances. The quality of the fines generated during HC and LC refining also differs. LC-refined pulps contain thinner fibrillar fines (thread-like) and HC-refined pulps broader fibrils such as lamellae-type fines. Flake-like fines from the outer fiber wall decreased in relative amount with energy input.

Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fibre technology point of view

During the last decade, major efforts have been made to develop adequate and commercially viable processes for disintegrating cellulose fibres into their structural components. Homogenisation of cellulose fibres has been one of the principal applied procedures. Homogenisation has produced materials which may be inhomogeneous, containing fibres, fibres fragments, fibrillar fines and nanofibrils. The material has been denominated microfibrillated cellulose (MFC). In addition, terms relating to the nano-scale have been given to the MFC material. Several modern and high-tech nano-applications have been envisaged for MFC. However, is MFC a nano-structure? It is concluded that MFC materials may be composed of (1) nanofibrils, (2) fibrillar fines, (3) fibre fragments and (4) fibres. This implies that MFC is not necessarily synonymous with nanofibrils, microfibrils or any other cellulose nano-structure. However, properly produced MFC materials contain nano-structures as a main component, i.e. nanofibrils.

Structure and properties of some natural cellulosic fibrils

This study examines the properties of cellulosic fibrillar fines manufactured from different pulp raw materials, bleached softwood kraft (BSWK), thermomechanical pulp (TMP), and non-wood sisal. Chemical characterisation showed that the carbohydrate and lignin contents of sisal were between those of BSWK and TMP. Sisal was found to contain about three times more calcium than showed that the solids content after immobilization was highest for the sisal suspension, followed by TMP and BSWK. This indicates that the dewatering ability of the fines suspension increased in the order BSWK, TMP and sisal. The loss modulus (G'') was maxmium with BSWK, indicating that the greatest viscous dissipation before immobilisation took place in the BSWK suspension. The strength properties of fines sheets decreased in the order BSWK, TMP and sisal. This is due to the highly fibrillated nature of BSWK fines, as illustrated by fibre saturation point (FSP), differential scanning calorimetric (DSC), and hydrodynamic specific volume (HSV) measurements.

Flocculation of papermaking fines by poly(ethylene oxide) and various cofactors: Effects of PEO entanglement, salt and fines properties

Papermaking fines are small pulp fiber fragments, which improve paper properties, such as paper strength and optical properties. They can be retained in a sheet of paper as fines aggregates or by deposition on fibers. Here we report on the flocculation of fines by a dual component flocculation system, consisting of poly(ethylene oxide) (PEO) and a cofactor. Previous studies showed that PEO is more effective when freshly dissolved than when well dissolved. This was ascribed to PEO entanglements present in freshly dissolved PEO, which disappear with time, shear or dilution. In this study the efficiencies of flocculation of thermomechanical pulp fines by entangled and disentangled PEO have been compared in the presence of different cofactors: a carboxylated phenolic resin (CPR), tannic acid (TA) and a sulfonated kraft lignin (SKL). The results support previous studies, showing that the state of entanglement of PEO has a significant effect on fines flocculation. In addition, we found that different cofactors affect disentangled PEO differently in response to salt addition and fines properties. When PEO was entangled, these cofactors caused the same high flocculation rate and the effect of the particle properties was negligible. When PEO was disentangled, the fines flocculation efficiency decreased to different levels for various cofactors, showing that CPR was superior to TA and SKL. The fibrillar fines and chunky fines were also flocculated at different rates by disentangled PEO/CPR, indicating the influence of particle properties. Adding salt prior to the cofactor and disentangled PEO improved the flocculation rate to the same level as entangled PEO at a given dosage when CPR was used as a cofactor.

Precipitated calcium carbonate (PCC) - cellulose composite fillers: Effects of PCC particle structure on the production and properties of uncoated fine paper

This work examines the precipitation of PCC – pulp composite fillers with varying crystal habits and their effects on the papermaking properties of printing and writing paper. Colloidal (c-PCC), rhombohedral (r-PCC), and scalenohedral types (s-PCC) of composite PCCs were produced and compared with commercial reference PCCs. Scanning electron micros-copy showed the c-PCC to be a high-surface-area nano-structured PCC. The rhombohedral composite was formed in clusters like a spider-web structure. Under similar experimental conditions, composite PCC was formed as individual ellipsoidal crystals and some of the particles had malformed structure, in contrast to the structured reference s-PCC. The co-precipitation and the structure of PCC significantly influence the forming, consolidation, and properties of paper, as well as its perform-ance in printing. Composite c-PCC showed the highest retention during forming. At higher filler contents, dewatering was reduced significantly with handsheets containing s- and r-PCC composite fillers. Colloidal composite hand-sheets showed the lowest tensile index and internal bond strength, while the rhombohedral composite gave the highest z-directional bond strength. Compared with the traditional reference samples containing commercial PCCs, paper with s- and r-composites had significantly higher density but similar light scattering ability. Addition of fibrillar fines to fine paper increased print rub fastness significantly in both laser and inkjet printed samples.

Fines Deposition on Pulp Fibers and Fines Flocculation in a Turbulent-Flow Loop

Fines retention is a combination of fines deposition on fibers and fines flocculation, followed by entrapment of fines flocs in a forming sheet. In the laboratory, fines flocculation is often studied in a dynamic drainage jar (DDJ) to mimic the hydrodynamic shear on a paper machine. However, the shear in a DDJ is very different from the shear on a machine. A flow geometry that might approximate shear in a headbox of a paper machine better is high Reynolds number flow through a tube because many headboxes contain a series of parallel pipes. We studied the deposition of fines and the flocculation of fines in a flow loop, with flow velocities on the order of a few meters per sceond, using a poly(ethylene oxide)-cofactor retention aid system. We found that fines deposition and flocculation follow the predictions of kinetic theories of Langmuir and Smoluchowski rather well despite the fact that fines are highly polydisperse. Fines were found to be flocculated even in the absence of a retention aid probably because of mechanical entanglements of fibrillar fines. Adding retention aids resulted in further aggregation. The detachment and floc breakup rates were found to be rather high, and extrapolation to papermaking conditions leads to the conclusion that fines deposition and flocculation are negligible in a headbox, at least for the retention aid system considered. This contradicts findings from DDJ experiments, which usually show appreciable fines retention. Perhaps a flow loop better represents flow conditions in a headbox, and a DDJ better represents flow conditions during drainage and formation.

Interaction between model colloidal wood resin, fillers and dissolved substances

This thesis presents studies of the interactions between suspended particles and dissolved and colloidal substances (DCS) in process water. The main focus has been to determine if colloidal wood resin is adsorbed by suspended fines or fillers, and how the dissolved material influences this adsorption. The effect of some synthetic polymers on this adsorption has also been investigated.Successive refining of mainly Norway spruce followed Successive refining of mainly Norway spruce followed by removal of the produced fines after each refining stage, resulted in fines with different physical and chemical properties. In the first refining stage mainly flake-like fines were produced, while more fibrillar fines were produced in later refining stages. The different types of fines were analysed for both the bulk and the surface composition. Variation in the chemical composition between the fines was particularly striking with regard to the surface composition. Special attention was also given to the amount and origin of charged groups since these may consume cationic additives in the papermaking process. After alkali treatment, between 80 and 90% of all the charged groups measured by polymer adsorption originated from three uronic acids.Fines were shown to adsorb model colloidal wood resin, but the adsorption was greatly influenced by the pH or salt content. Also the amount of dissolved components in the suspension, which sterically stabilised the colloidal wood resin, was shown to strongly influence the adsorption of the colloidal wood resin to the fines. The flake-like fines adsorbed the colloidal wood resin to a higher extent than the fibrillar fines. This selectivity was also possible to obtain by using polyethyleneoxide (PEO). PEO removed the sterically stabilised colloidal wood resin more efficiently when flake-like fines rather than fibrillar fines were present. For comparison, cationic polyacrylamide (CPAM) did not have this selectivity. The selectivity of PEO was explained by a higher affinity to flake-like fines than fibrillar fines. It was shown that more PEO adsorbed to flake-like fines rather than to fibrillar ones. PEO may adsorb to extractive surfaces, but was inhibited by adsorbed components from the dissolved fraction. The degree of stabilisation was also shown to influence the adsorption of the colloidal wood resin by other particles like fillers. This adsorption, which was energetically favourable, did not occur at high concentrations of dissolved material.

The effect of dissolved substances on the adsorption of colloidal extractives to fines in mechanical pulp

This thesis presents studies of the interactions between suspended particles and dissolved and colloidal substances (DCS) in process water. The main focus has been to determine if colloidal wood resin is adsorbed by suspended fines or fillers, and how the dissolved material influences this adsorption. The effect of some synthetic polymers on this adsorption has also been investigated.Successive refining of mainly Norway spruce followed Successive refining of mainly Norway spruce followed by removal of the produced fines after each refining stage, resulted in fines with different physical and chemical properties. In the first refining stage mainly flake-like fines were produced, while more fibrillar fines were produced in later refining stages. The different types of fines were analysed for both the bulk and the surface composition. Variation in the chemical composition between the fines was particularly striking with regard to the surface composition. Special attention was also given to the amount and origin of charged groups since these may consume cationic additives in the papermaking process. After alkali treatment, between 80 and 90% of all the charged groups measured by polymer adsorption originated from three uronic acids.Fines were shown to adsorb model colloidal wood resin, but the adsorption was greatly influenced by the pH or salt content. Also the amount of dissolved components in the suspension, which sterically stabilised the colloidal wood resin, was shown to strongly influence the adsorption of the colloidal wood resin to the fines. The flake-like fines adsorbed the colloidal wood resin to a higher extent than the fibrillar fines. This selectivity was also possible to obtain by using polyethyleneoxide (PEO). PEO removed the sterically stabilised colloidal wood resin more efficiently when flake-like fines rather than fibrillar fines were present. For comparison, cationic polyacrylamide (CPAM) did not have this selectivity. The selectivity of PEO was explained by a higher affinity to flake-like fines than fibrillar fines. It was shown that more PEO adsorbed to flake-like fines rather than to fibrillar ones. PEO may adsorb to extractive surfaces, but was inhibited by adsorbed components from the dissolved fraction. The degree of stabilisation was also shown to influence the adsorption of the colloidal wood resin by other particles like fillers. This adsorption, which was energetically favourable, did not occur at high concentrations of dissolved material.

Homo- and heteroflocculation of papermaking fines and fillers

The effects of cationic polyethylenimine (PEI) on the colloidal stability of anionic fines (microcrystalline cellulose or thermomechanical fines), fillers (clay) and their mixtures in deionized and tap water were investigated, using a photometric dispersion analyzer. Measurements confirmed that PEI flocculates all used materials by charge neutralization. As expected, higher additions of PEI lead to electrostatic stabilization of microcellulose and clay suspensions, but it was not possible to stabilize the suspension of fines using high additions of PEI. This is ascribed to the mechanical entanglements of fibrillar fines. In tap water, much more PEI is needed to reach optimum flocculation conditions than in deionized water. Heteroflocculation between PEI-coated clay and fines takes place with a rate which, for high fines concentration and a constant clay concentration, is independent of fines concentration. A theoretical model for the heteroflocculation of fines with PEI-coated clay has been developed, which explains the observed trends. In essence, clay particles can act as bridging agents for fines flocculation.

The charge and chemical composition of fines in mechanical pulp

This thesis presents studies of the interactions between suspended particles and dissolved and colloidal substances (DCS) in process water. The main focus has been to determine if colloidal wood resin is adsorbed by suspended fines or fillers, and how the dissolved material influences this adsorption. The effect of some synthetic polymers on this adsorption has also been investigated.Successive refining of mainly Norway spruce followed Successive refining of mainly Norway spruce followed by removal of the produced fines after each refining stage, resulted in fines with different physical and chemical properties. In the first refining stage mainly flake-like fines were produced, while more fibrillar fines were produced in later refining stages. The different types of fines were analysed for both the bulk and the surface composition. Variation in the chemical composition between the fines was particularly striking with regard to the surface composition. Special attention was also given to the amount and origin of charged groups since these may consume cationic additives in the papermaking process. After alkali treatment, between 80 and 90% of all the charged groups measured by polymer adsorption originated from three uronic acids.Fines were shown to adsorb model colloidal wood resin, but the adsorption was greatly influenced by the pH or salt content. Also the amount of dissolved components in the suspension, which sterically stabilised the colloidal wood resin, was shown to strongly influence the adsorption of the colloidal wood resin to the fines. The flake-like fines adsorbed the colloidal wood resin to a higher extent than the fibrillar fines. This selectivity was also possible to obtain by using polyethyleneoxide (PEO). PEO removed the sterically stabilised colloidal wood resin more efficiently when flake-like fines rather than fibrillar fines were present. For comparison, cationic polyacrylamide (CPAM) did not have this selectivity. The selectivity of PEO was explained by a higher affinity to flake-like fines than fibrillar fines. It was shown that more PEO adsorbed to flake-like fines rather than to fibrillar ones. PEO may adsorb to extractive surfaces, but was inhibited by adsorbed components from the dissolved fraction. The degree of stabilisation was also shown to influence the adsorption of the colloidal wood resin by other particles like fillers. This adsorption, which was energetically favourable, did not occur at high concentrations of dissolved material.

Solid phase extraction (SPE) of hydrophobic components from a model white water

This thesis presents studies of the interactions between suspended particles and dissolved and colloidal substances (DCS) in process water. The main focus has been to determine if colloidal wood resin is adsorbed by suspended fines or fillers, and how the dissolved material influences this adsorption. The effect of some synthetic polymers on this adsorption has also been investigated.Successive refining of mainly Norway spruce followed Successive refining of mainly Norway spruce followed by removal of the produced fines after each refining stage, resulted in fines with different physical and chemical properties. In the first refining stage mainly flake-like fines were produced, while more fibrillar fines were produced in later refining stages. The different types of fines were analysed for both the bulk and the surface composition. Variation in the chemical composition between the fines was particularly striking with regard to the surface composition. Special attention was also given to the amount and origin of charged groups since these may consume cationic additives in the papermaking process. After alkali treatment, between 80 and 90% of all the charged groups measured by polymer adsorption originated from three uronic acids.Fines were shown to adsorb model colloidal wood resin, but the adsorption was greatly influenced by the pH or salt content. Also the amount of dissolved components in the suspension, which sterically stabilised the colloidal wood resin, was shown to strongly influence the adsorption of the colloidal wood resin to the fines. The flake-like fines adsorbed the colloidal wood resin to a higher extent than the fibrillar fines. This selectivity was also possible to obtain by using polyethyleneoxide (PEO). PEO removed the sterically stabilised colloidal wood resin more efficiently when flake-like fines rather than fibrillar fines were present. For comparison, cationic polyacrylamide (CPAM) did not have this selectivity. The selectivity of PEO was explained by a higher affinity to flake-like fines than fibrillar fines. It was shown that more PEO adsorbed to flake-like fines rather than to fibrillar ones. PEO may adsorb to extractive surfaces, but was inhibited by adsorbed components from the dissolved fraction. The degree of stabilisation was also shown to influence the adsorption of the colloidal wood resin by other particles like fillers. This adsorption, which was energetically favourable, did not occur at high concentrations of dissolved material.